Ecological Classification System

Red River Prairie Subsection

The western boundary of this subsection is
the Red River of the north. The eastern boundary follows the eastern
limits of continuous tall grass prairie vegetation at the time of Euro-American settlement. Portions
of a till plain (Fergus Falls Till Plain [Dept. of Soil Science, 1969 and
1980a]) are included. The southern boundary lies at the southern end
of the till plain and the Glacial Lake Agassiz basin.

The majority of this subsection is a glacial lake
plain with silty, sandy, and clayey lacustrine deposits. It is level, uniform,
and featureless, broken only by wetlands, meandering waterways, and old
beach ridges. Drainage is to the north via the Red River and its tributaries.

Landform

The major landform is a large lake plain (Glacial Lake Agassiz).
Minor landforms include a till plain, beach ridges, sand dunes, and water-reworked till. The greatest depth of lake laid sediments is present along
the Red River, which forms the west boundary. Lacustrine origin sediments
thin to the east, where glacial till was leveled and reworked with little
deposit of lacustrine sediments. Topography is level to gently rolling.
There is some steeper topography along drainages and adjacent to Lake Traverse.

Bedrock geology

Throughout the subsection there are
200-400 feet of glacial drift overlying bedrock (Olsen
and Mossler 1982). Glacial drift is underlain by Precambrian bedrock in
the east. The western part is underlain by Cretaceous, Ordovician, and
Jurassic sedimentary bedrock (Morey et al. 1982). There are bedrock exposures
along the shores of Lake Traverse in the southwest. These are sedimentary
bedrock and contain many fossils.

Soils

Poorly, somewhat poorly, and moderately well-drained lacustrine
clays, silts, and sands make up the majority of soils in this subsection.
They are primarily Mollisols; Cummins and Grigal (1981) map most of these
soils as Aquolls (wet Mollisols). Borolls (cold, dry Mollisols) are also
common. Virtually all of the poorly drained soils have been ditched and
drained for agricultural use. Saline soils are present in localized areas.
Dry, sandy and gravelly soils are characteristic of the beach ridges present
throughout the subsection.

Climate

Total precipitation ranges from 21 inches in the northwest to
23 inches in the east, with roughly 40% occurring during the growing season.
The growing season ranges from 111 to 136 days and is longest in the south.
The climate of the subsection is influenced by Pacific Maritime, Gulf, and Polar air masses; the polar
air mass has more regular impact upon this subsection than does the Gulf
air mass (Critchfield 1974).

Hydrology

This subsection is drained by the Red River, which
forms the west boundary. The Red River flows north into Canada. The drainage
network is minimally developed. Rivers and streams meander
extensively. Flooding is common in early
spring and can cause major problems due to level topography. Frozen conditions
to the north can cause water to back up and flood large areas. There are
few lakes present. Lakes are most common on a till plain in the southeast and
characteristically, are shallow and perched.

Presettlement vegetation

Tallgrass prairie and wet prairie were the dominant vegetation before settlement (Marschner, 1974). The upland prairie was dominated by bluestems,
Indian grass, and several other grasses. Wet prairie was dominated by bluejoint
grass, cordgrass, cattails, rushes, and sedges. Narrow, forested floodplains
were common along larger streams and rivers. Broader zones of woodland
or brushland were common in "fire shadows" along streams; size
and configuration depended on prevailing wind and stream alignment (Robert
Dana, personal communication).

Present vegetation and land use

The
most important land use is agriculture. The lake plain has been intensively
ditched for agriculture. Native flora persists in fragments (in some
of moderate size) east of the beach ridges and in the interbeach zone (Albert
1993).

Natural disturbance

Fire, drought, and annual flooding
are important. High wind events (tornados and straight-line winds) are
also common. Historically, bison grazing and ant activity caused important
modifications of the vegetation and soils respectively (Albert 1993).